Ignition arrangement for internal combustion engines having an alternating current generator

ABSTRACT

Shunted across the charging winding of the alternating current generator is an impedance and a spark discharge capacitor connected in series. A thyristor is connected to permit discharge of the capacitor through the primary winding of the spark core when the thyristor is conductive, the control electrode of the latter being connected to the impedance so that the triggering voltage is the voltage drop across the impedance.

United States Patent Wesemeyer [541 IGNITION ARRANGEMENT FOR INTERNALCOMBUSTION ENGINES HAVING AN ALTERNATING CURRENT GENERATOR [72]Inventor: Jurgen Wesemeyer,

Vaihingen, Germany [73] Assignee: Robert Bosch GmbH, Stuttgart,-Germany[22] Filed: Jan. 15, 1971 [21] Appl. No.: 106,674

Stuttgart- [30] Foreign Application Priority Data [451 Dec.5, 1972Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort FlintAttorney-Michael S. Striker [57] ABSTRACT Shunted across the chargingwinding of the alternating current generator is an impedance and a sparkdischarge capacitor connected in series. A thyristor is Jan. 20, 1970Germany ...P 20 02 310.3 connected to Permit discharge of the capacitorthrough the primary winding of the spark core when [52] U.S. Cl..123/148 E, 123/149 R the thyri is n ti th ntr l el tr de of [51] Int.Cl ..F02p 3/06 the latter being connected to the impedance so that [58]Field of Search ..123/148 E the triggering voltage is the voltage dropacross the impedance. [56] References Cited 16 Claims, 3 Drawing FiguresUNITED STATES PATENTS 3,367,314 9/1965 l-lirosawa et al. ..123/148 E F"i I PATENTEDIIEB 191 3. 704,700

Fig.3

INVENTOR ATTORNEY IGNITION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINESIIAVING AN ALTERNATING CURRENT GENERATOR BACKGROUND OF THE INVENTION Theinvention relates to an ignition arrangement for internal combustionengines, the arrangement having a spark discharge capacitor that ischarged by the alternating current generator and discharged, at theignition point, through the primary of the spark plug, by an electronicswitch.

With these known arrangements it is essential to trigger the electronicswitch-usually a transistor, a thyristor, or a triac-by a controlvoltage conducted to the switch at the ignition time. The requiredcontrol voltage is obtained from a battery ora generator, and isconducted by a mechanical or an electronic control switch at the correcttime to'the control electrode of the transistor or thyristor. Theprior'art also discloses circuits for connecting the control electrodeof a' thyristor to a pulse generator having magnets, the pulse generatordelivering a voltage pulse at the ignition point to trigger thethyristor.

These solutions have the disadvantage that special and sometimes troubleprone, arrangements are neces- SUMMARY OF THE INVENTION 7 An object ofthe invention is an ignition arrangement that solves, in a very simplemanner, the problem of obtaining the triggering voltage from thecharging circuit and conducting this voltage to the control electrode ofthe electronic switch at the desired time.

The invention consists essentially of an alternating current generator,a capacitor connected to the alternating current generator to be chargedthereby, a spark coil having a primary winding and a secondary winding,the latter winding being connected to at least one spark plug,electronic switch means triggered into conductivity bya control voltage,the electronic switch means being connected between the capacitor andthe primary winding so that when the electronic switch means isconductive the capacitor is free to discharge through the primarywinding to induce in the secondary winding a voltage pulse sufficient tospark the plug, and impedance means connected in series with thecapacitor for causing a voltage gap, that is, the control voltage, theresistive-or the reactive component of the impedance means having anyvalue including zero.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. v

The invention itself, however, both as to its construction and itsmethod of operation, will be'best understood from the followingdescription of specific embodiments when read in connection with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of theignition arrangement of the invention;

FIG. 2 is a vector diagram showing the phase relationships between thecharging current and the voltages across the capacitor, the impedance,and the charging winding; and

. FIG. 3 shows the time relationships of the current and of the voltagesof the vector diagram of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1 theignition arrangement of the invention is energized by an alternatingcurrent generator 10, in the charging winding 1 1 of which there isinduced analternating voltage by the rotation of a bar having permanentmagnets, the bar 12 being driven by the internal combustion engine, notshown. A lead 13 connects one end of the charging winding 11 to oneplate of a spark discharge capacitor 14 and to respective ends of theprimary winding 15 and the secondary winding 16 of a spark coil 17. Aspark plug wire 18 connects the other end of the secondary winding to aspark plug 19. A lead 20 connects the other end of the primary winding15 to the anode of a thyristor 21, which latter acts as an electronicswitch. The cathode of the thyristor is connected by a lead 25 to thejunction between the capacitor 14 and an impedance 22, the impedance.and the capacitor being connected in series. Components 20, 21 and 25constitute discharge current path means connecting capacitor 14 withprimary winding 15. A lead 23 connects the series connected impedanceand capacitor to the other end of the charging winding 11. Thetriggering voltage for the control electrode 26 of the thyristor isconducted by a lead 24, connected between the control electrode and theend of the impedance remote from the capacitor.

When the internal combustion engine operates, there is induced in thecharging winding 11 of the generator 10 an alternating current voltage,which, so long as the thyristor 21 is non-conductive,-causes a currentto flow in the capacitor charging circuit, the magnitude and phase ofthis current depending on the total impedance of the charging circuit.FIG. 2 is a vector diagram of the current and voltages in the chargingcircuit. It will be assumed that the instantangeous positive value ofthe voltage U induced in the winding 11 is 150' volts, that theresistance of the impedance 22 is approximately 50 ohms, and that thecapacitor 14 is l microfarad. With these assumptions, the chargingcurrent I of approximately 200 milliamperes leads the voltage U byapproximately 82". The voltage drop U across the impedance 22 isapproximately 10 volts and is in phase with the current I The voltage Uacross the capacitor 14 is approximately 148 volts, and it lags thevoltage U by and the voltage U by 8.

The spark discharge capacitor i4 is charged and discharged at thefrequency of the alternating voltage U induced in the charging winding11. In order to assure a maximum voltage at the sparkplug 19 it isessential that the capacitor is discharged as nearly as possible whenthe capacitor voltage U is at its maximum positive value. This conditionis ensured by using, for the thyristor triggering voltage, the negativepart of the voltage U across the impedance 22. In FIG. 3, the currentand voltages in the charging circuit are plotted along the upper timeaxis and the thyristor triggering voltage U, is plotted along the lowertime axis t Since thetriggering voltage U, is measured from the cathodeof the thyristor, it is the negative of the voltage U As FIG. 3 shows,at this moment the voltage U,, across the capacitor. 14 has fallen verylittle from its peak value, so that very nearly the maximum possibleamount of stored electrical energy is discharged through the thyristor21 and the primary winding 15 of the spark plug". The highvoltageinduced in the secondary 16 causes a first spark at the spark plug 19Since a positive voltage U is induced in the charging winding 11 at themoment capacitor 14 begins to discharge, the latter is immediatelyrecharged after being discharged and then again discharged during asecondary firing Nz thereby producing one or more sparks of rapidlydecreasing energy, at the plug 19. This charging and discharging of .thecapacitor 14 is repeated during each period of the .voltage, induced inthe charging winding 11; the ignition occurs at the frequency of thegenerator, which frequency is dependent on' the motor rpm.

The impedance 22 is a voltage dependent component, inorder to avoidexceeding the maximum permissible triggering voltage at high speeds ofthe internal combustion engine. As shown in FIG. 1, the impedance 22 canbe made adjustable to enable shifting of the ignition point independenceon the motor rpm or the motor load. The resistive or reactive componentof the impedance can have any value including zero. The reactivecomponent can be inductive and/or capacitive. By changing the value ofthe impedance 22, the magnitude and phase of U R are changed, and theignition point Zzp is shifted, at which point the triggering voltage U,is equal to the triggering voltage U of the thyristor 21.

in accordance with the invention, a semiconductor,

such as a Zener diode, can be used as the impedance 22.

' It is advantageous to construct the capacitor 14, thyristor 21, andthe impedance 22 as a replaceable subunit. With this in view, the lead13 can be omitted, and the respective terminals of the charging winding11, capacitor 14, primary 15, and secondary 16 connected to ground.

It will be understood that each of the elements described above, 'or twoor more together, may also find a useful application in other types ofcircuits differ- Y ing from the types described above.

While the invention has been illustrated and described as embodied inignition arrangement for internal combustion engines having analternating current generator, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in an way from the spirit of the presentinvention.

Without furtheranalysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat,from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and-desired to be protected by Letters Patent isset forth in the appended claims.

lclairn:

l. Anignition arrangement adapted to activate at least one spark plug ofan internal combustion engine, comprising, in combination ignitioncapacitor means; A.C. generator means; capacitor current path meansconnecting said generator means with said capacitor means for supplyingalternating current thereto; transformer means'having a primary windingand a secondary winding; discharge current path means connecting saidcapacitor means with said primary winding and including electronicswitch. means having control electrode means and controlling currentflow from said capacitor means through said path means as a function ofthe voltages at said control electrode means; and impedance meansarranged in said capacitor current path means connected in series withsaid capacitor means and connected with said control electrode means,the voltage across said impedance means determining the voltages at saidcontrol electrode means, and thereby through said capacitor means in onedirection and alternately in opposite direction, thereby alternatelyincreasing and decreasing the voltage across said capacitor means.

3. An arrangement as defined in claim 1, wherein said A.C. generatormeans produces current flow through said capacitor means and impedancemeansin one direction, producing across said impedance means a voltagedrop preventing current flow through said switch-means, and alternatelyproduces current flow through said capacitor means and impedance meansin opposite direction, producing across said impedance means a voltagedrop permitting current flow through said switch means. j

,4. An arrangement as defined in claim 1, said switch means comprisingthyristor means.

5. An arrangement as defined in claim 3, said switch means comprisingthyristor means having a gate and a cathode together constituting saidcontrol electrode means. I

6. An arrangement as defined in claim 1, wherein said generator meansproduces during each voltagecycle out-of-phase first and second' voltagedrops across said capacitor means and said impedancemeans, respectively,and wherein said first voltage drop varies between minimum and maximumvalues, and wherein said second voltage drop varies between valuesrespectively permitting and preventing current flow through said switchmeans, and further wherein said second voltage drop reaches a valuepermitting current flow through said switch means a fraction of avoltagecycle after said first voltage drop reaches said maxwherein saidimpedance means has one terminal connected with one terminal of saidgenerator means and with said gate and another terminal connected withone terminal of said capacitor means and with said cathode, and whereinsaid primary winding has one terminal connected to said anode. I

8. An arrangement as defined in claim 7, wherein the other terminal ofsaid capacitor means is connected to the other terminal of saidgenerator means, to the other terminal of said primary winding, to oneterminal of said secondary winding, and to ground.

9. An arrangement as defined in claim l, wherein said impedance meanshas a voltage-dependent resistive component.

10. An ignition arrangement as defined in claim 1, wherein saidgenerator means includes a charging winding, said series connectedcapacitor and impedance means being connected in parallel with said 11.An ignition arrangement as defined in claim 1, wherein said capacitor,means electronic switch means and impedance means compose a replaceablesubunit of the ignition arrangement.

12. An ignition arrangement as defined in claim 1, wherein saidimpedance means is adjustable.

13. An ignition arrangement as defined in claim 1, wherein saidimpedance means includes inductively and capacitively reactivecomponents.

14. An ignition arrangement as defined in claim 1, wherein saidimpedance means includes an inductively reactive component.

15. An ignition arrangement as defined in claim 1, wherein saidimpedance means includes a capacitively reactive component.

16. An ignition arrangement as defined in claim 1', wherein saidimpedance means is atleast predominantly resistive.

1. An ignition arrangement adapted to activate at least one spark plugof an internal combustion engine, comprising, in combination ignitioncapacitor means; A.C. generator means; capacitor current path meansconnecting said generator means with said capacitor means for supplyingalternating current thereto; transformer means having a primary windingand a secondary winding; discharge current path means connecting saidcapacitor means with said primary winding and including electronicswitch means having control electrode means and controlling current flowfrom said capacitor means through said path means as a function of thevoltages at said control electrode means; and impedance means arrangedin said capacitor current path means connected in series with saidcapacitor means and connected with sAid control electrode means, thevoltage across said impedance means determining the voltages at saidcontrol electrode means, and thereby determining the current flow fromsaid capacitor means through said discharge current path means.
 2. Anarrangement as defined in claim 1, wherein said A.C. generator meansproduces current flow through said capacitor means in one direction andalternately in opposite direction, thereby alternately increasing anddecreasing the voltage across said capacitor means.
 3. An arrangement asdefined in claim 1, wherein said A.C. generator means produces currentflow through said capacitor means and impedance means in one direction,producing across said impedance means a voltage drop preventing currentflow through said switch means, and alternately produces current flowthrough said capacitor means and impedance means in opposite direction,producing across said impedance means a voltage drop permitting currentflow through said switch means.
 4. An arrangement as defined in claim 1,said switch means comprising thyristor means.
 5. An arrangement asdefined in claim 3, said switch means comprising thyristor means havinga gate and a cathode together constituting said control electrode means.6. An arrangement as defined in claim 1, wherein said generator meansproduces during each voltage-cycle out-of-phase first and second voltagedrops across said capacitor means and said impedance means,respectively, and wherein said first voltage drop varies between minimumand maximum values, and wherein said second voltage drop varies betweenvalues respectively permitting and preventing current flow through saidswitch means, and further wherein said second voltage drop reaches avalue permitting current flow through said switch means a fraction of avoltage-cycle after said first voltage drop reaches said maximum value.7. An arrangement as defined in claim 1, said capacitor means, impedancemeans, primary winding, secondary winding and generator means eachhaving two terminals, and wherein said switch means comprises athyristor having an anode, a cathode and a gate, and wherein saidimpedance means has one terminal connected with one terminal of saidgenerator means and with said gate and another terminal connected withone terminal of said capacitor means and with said cathode, and whereinsaid primary winding has one terminal connected to said anode.
 8. Anarrangement as defined in claim 7, wherein the other terminal of saidcapacitor means is connected to the other terminal of said generatormeans, to the other terminal of said primary winding, to one terminal ofsaid secondary winding, and to ground.
 9. An arrangement as defined inclaim 1, wherein said impedance means has a voltage-dependent resistivecomponent.
 10. An ignition arrangement as defined in claim 1, whereinsaid generator means includes a charging winding, said series connectedcapacitor and impedance means being connected in parallel with saidgenerator means.
 11. An ignition arrangement as defined in claim 1,wherein said capacitor, means electronic switch means and impedancemeans compose a replaceable subunit of the ignition arrangement.
 12. Anignition arrangement as defined in claim 1, wherein said impedance meansis adjustable.
 13. An ignition arrangement as defined in claim 1,wherein said impedance means includes inductively and capacitivelyreactive components.
 14. An ignition arrangement as defined in claim 1,wherein said impedance means includes an inductively reactive component.15. An ignition arrangement as defined in claim 1, wherein saidimpedance means includes a capacitively reactive component.
 16. Anignition arrangement as defined in claim 1, wherein said impedance meansis at least predominantly resistive.